The present invention relates to a luminescence display panel using discharge gas for use with television and computer systems, for example.
FIG. 6 illustrates a conventional luminescence display panel using discharge gas, generally indicated by reference numeral 20, for use preferably with a plasma display system. The panel 20, including transparent front and rear plates, 21 and 22, spaced apart from each other, is depicted so that one surface 23 of the front plate, away from the rear plate 22, is oriented upward.
Also, FIG. 7 illustrates an enlarged partial schematic view of an AC plasma display panel, which is an example of such luminescent display panels. As shown, the panel 20 includes a discharge chamber 3 between the front and rear plates, 21 and 22. The other surface of the front plate 21, opposing the rear plate 22, supports a plurality of pairs of elongated scanning and maintaining electrodes, 6 and 7, extending in a parallel fashion. The electrodes, 6 and 7, are covered with a dielectric layer 4 and further with a protection layer 5, positioned away from the front plate 21. The rear plate 22 supports a plurality of elongated data electrodes 8 each extending perpendicular to the scanning and maintaining electrodes, 6 and 7, in a parallel fashion. Also supported on the rear plate 22 are a plurality of elongated partitions 9 each extending in parallel to and spaced a certain distance from the data electrodes 8, so that the discharge chamber 3 is formed between neighboring partitions 9. A phosphor 10 is provided between the neighboring partitions 9 so that it covers both data electrode 8 and opposing side surfaces of the partitions 9 in the discharge chamber 3. For clarity of the drawing, the phosphor 10 is illustrated only in part. Each discharge chamber 3 is filled with a gas mixture having xenon and at least one inert, as such as helium, neon, or argon.
In operation, an electric discharge is generated between the scanning and maintaining electrodes, 6 and 7, in the discharge chamber 3. This excites the phosphor 10 to emit visible light, which is used for displaying an image to be viewed on the front plate 21.
Referring to FIG. 8, which is a cross-sectional view taken along lines VIIIxe2x80x94VIII in FIG. 7, descriptions will be made to the light emission. As shown, three neighboring phosphors 10 construct different color elements of each pixel, red light element 10R, green light element 10G and blue light element 10B for emitting red, green, and blue lights, respectively.
When the electric discharge 1 has occurred in the discharge chamber 3, the ultraviolet light 2 generated by the discharge 1 excites the phosphor 10. This allows the color elements 10R, 10G, and 10B to emit red, green, and blue light, respectively, as shown by dotted lines in FIG. 8. It should be understood that the light passes are provided by dotted lines in FIG. 8, as well as in other drawings, only for illustration.
FIG. 9, which is also a cross-sectional view taken along lines VIIIxe2x80x94VIII in FIG. 7, illustrates passes of red light emitted only from the color element 10R. In this instance, the emitted red light RO and R1 passes through the front plate 21 and then projects out toward a viewer. Simultaneously, the red light R1 projected obliquely to the front plate 21 is in part reflected at an inner surface 21a of the front plate 21 and then at the neighboring green element 10G. The reflected red light is then projected in part through the front plate 21, which is shown at R2. Remaining red light is reflected at the surface 21 a of the front plate 21 and then at the neighboring blue element 10B and, afterwards, projected through the front plate 21. Likewise, the light emitted obliquely is transmitted transversely and reflected on the green and blue elements, 10G and 10B, which results in an undesirable halation of the red light being projected through the front plate 21 to the viewer.
Also, the red light emitted from the back surface of the red element 10R is reflected at the inner surface of the rear plate 22 and then transmitted in part through the neighboring green element 10G, which is finally projected through the front plate 21 as shown at R4. Further, the red light reflected at the green element 10G is further reflected at the surfaces 22b and then 22a of the backing and then transmitted through the blue element 10B, which is finally projected through the front plate 21 as shown at R5. As such, another undesirable halation of the red light is projected through the front plate 21 to the viewer. This results in a degradation of a color contrast of the plasma display panel.
In addition, as shown in FIG. 10, which is also a cross-sectional view of taken along lines VIIIxe2x80x94VIII in FIG. 7, when the red and green elements, 10R and 10G, simultaneously emit respective lights, the green lights GO and G1 are merged with the red light halation, R2 and R4, which degrades purity of the green color. At this moment, the red light is also merged with the green light, which also results in a degradation of the red color.
The halation can be evaluated. For example, as shown in FIG. 11A, in the evaluation, all the color elements on the left side of the AC plasma display panel are turned on to present a white image and, on the other hand, all the color elements on the right side are turned off to present a black image. Then, measured is a variation of brightness in a boundary zone between the left turned-on and right turned-off regions. When no halation is assumed to occur, the left side region (L less than 0) would provide 100% brightness in white and the right side region 0% brightness in black (L greater than 0). Contrary to this, practically, as shown in FIG. 11B, although in the conventional AC plasma display 100% brightness is obtained in the left side turned-on region (L less than 0), the brightness in the right side turned-off region decreases gradually from the boundary line and then 0% brightness in black is obtained at a portion spaced a certain distance P away from the boundary line. Also, the distance P in which the brightness decreases from 100% to 0% is significantly large in the conventional AC plasma display panel. Therefore, the boundary line between the white and black regions is unclear due to the halation. This in turn deteriorates a color contrast purity of each color.
To overcome this problem, a luminescence display panel using discharge gas of the present invention includes dark front and rear plates. Preferably, darkness of each plate is equal to at least about 20%. Instead, transparency of each plate may be equal to at most about 80%. This allows the halation to be decreased considerably in the luminescence display panel of the present invention.